The 3rd Generation Partnership Project (3GPP) is responsible for the standardization of the Universal Mobile Telecommunication System (UMTS) and the fourth-generation wireless system commonly known as Long Term Evolution (LTE). The 3GPP work on LTE is also referred to as Evolved Universal Terrestrial Access Network (E-UTRAN). LTE is a technology for realizing high-speed packet-based communication that can reach high data rates both in the downlink and in the uplink, and is thought of as a next generation mobile communication system, relative to UMTS. In order to support high data rates, LTE allows for a system bandwidth of 20 MHz, or up to 100 Hz when carrier aggregation is employed. LTE is also able to operate in different frequency bands and can operate in at least Frequency Division Duplex (FDD) and Time Division Duplex (TDD) modes.
In a future “Networked Society” scenario there are expected to be a very large number of machine-type-communication (MTC) devices supported by wide-area wireless networks. Many of these devices will transmit a small amount of uplink data, e.g., 100 bits or so, very infrequently, e.g., once per hour.
Some MTC devices may be installed in locations that are inaccessible to or only occasionally used by people, and which may not have robust coverage from traditional wireless networks. 3GPP, in its continuing standardization of technology for LTE, plans to introduce a new solution for “enhanced MTC coverage,” with a goal of improving the link budget under enhanced MTC coverage by approximately 15-20 dB, compared to what is supported with the legacy LTE standard. (See, for example, 3GPP Tdoc RP-121441, available at http://www.3gpp.org/ftp/tsg_ran/TSG_RAN/TSGR_57//Docs/.) This is expected to make LTE even more attractive for MTC type of solutions.
Machine-to-machine (M2M) communication, also known as machine-type communication (MTC), is used for establishing communication between machines and between machines and humans. The communication may comprise an exchange of data, signaling, measurement data, configuration information, etc. The device sizes may vary from that of a wallet to that of a base station. M2M devices are quite often used for applications like sensing environmental conditions (e.g., temperature reading), metering or measurement (e.g., electricity usage, etc.), fault finding or error detection, etc. In these applications, the M2M devices are active very infrequently, but over a particular duration that depends upon the type of service, e.g., about 200 milliseconds once every 2 seconds, about 500 milliseconds every 60 minutes, etc.
Machine-type-communication (MTC) involves the monitoring of dynamical systems in many cases, such as vehicle-to-vehicle communications, industrial control applications, and machine-to-machine communications. The communication involved in these applications generally includes messaging of the current state of the monitored system, which is dynamical, i.e., changing in time.
The current state in a dynamical system is dependent on the past states. As a result, knowledge about past states for the system can be used to improve an estimate of the current state. Generally, more information regarding the system's past states allows more accurate estimation of the system's present state. However, due to memory limitations, it is often desired that only a small portion of the system's entire state history is stored. This may be a particular issue in MTC applications, where the resources of a given device may be limited.
The dynamical nature of the systems monitored in MTC applications may be exploited to improve the encoding and decoding of the messages sent to indicate the systems' current states. Encoding and decoding techniques that do this while using as little memory as possible for storing prior state information are needed.